To address global disparities in trauma care, the World Health Organization (WHO) Essential Trauma Care Guidelines outline the “needs of the injured patient,” such as airway management and bleeding control, as essential health services for all people regardless of resources or context. The mandate of health systems to provide essential services has also been stressed through the rights-based approach to health 
. The availability of adequate emergency medical services is often considered a basic human right in high-income countries 
and this right should not be neglected in low and middle income countries which bear the disproportionate burden of injury. In addition, calls for injury research in resource-constrained settings have particularly stressed the need for intervention-based research 
Our study thus fills these critical needs. Despite a substantial burden of injury in Uganda, Kampala, its largest city, has no formal prehospital emergency system. We found that lay people can effectively retain knowledge of prehospital trauma care learned through a context-appropriate first-aid course for at least six months. Trainees found this basic intervention useful and after the training, were able to more confidently deploy these new skills. Our findings suggest that police may be the ideal first-responders in Kampala given their higher knowledge retention and skills and supply use compared with other trainees. Their established communication and transportation networks are also an advantage. However, appropriate recognition for such services will be critical to dissuade any incentive to charge informal fees for services. This study also showed shorter times from injury to hospital arrival, although this compares two different datasets; our prospectively collected encounter records and the hospital trauma registry. Nonetheless, the findings suggest that delivery of prehospital care did not delay access to care.
This study can be compared with others' experiences in developing prehospital systems in resource-constrained settings. In urban Ghana, truck drivers who completed a similar context-appropriate first-aid course showed a significant increase in skill use at 10 months based on response rate of 28% 
. However, trainees assembled first-aid kits at their own expense and at 10 months, only 27% of trainees carried materials useful for universal precautions such as gloves or plastic bags. Our study conducted more in-depth and periodic assessments of participants' fund of knowledge and use of free first-aid kits.
Husum et al. have demonstrated a 15% reduction in mortality of war and landmine victims in Iraq and Cambodia where paramedics and lay first-responders were trained to provide prehospital trauma care 
. Despite extensive training programs for both groups, most prehospital care provided was solely basic life support. Others have argued for implementation of this model in non-conflict settings without formal emergency systems 
. We designed our study based on a belief that a simple “scoop-and-run” approach with basic life-saving interventions will be most practical and effective in the absence of second-tier responders such as paramedics who are trained in advance airway management, vascular access and fluid resuscitation. In addition, we could not provide extensive training for our participants due to opportunity costs of removing police officers from duty and imposing a greater loss of income for the taxi drivers. Therefore, while not directly comparable to previous work, our study suggests that high knowledge retention and greater use of first-aid skills may be rough proxies for improvements in trauma care.
We also estimated that the costs of scaling up this intervention to cover all of Kampala's 1.2 million people was $25–150 per life year saved ($598–$3596 per death averted) which is comparable to the costs of traffic enforcement in Kampala at $27 per life year saved 
or the distribution of antiretroviral medications for HIV in Uganda at $600 per life year saved 
. As such, this intervention could be considered very cost-effective. Additionally, Uganda's health policy is based on a minimum package of essential health services, which was initially costed at $34 per capita by the WHO 
. Current public expenditure on health is USD $22 per capita in Uganda 
. Thus, $0.12 per capita would be a modest price to pay for prehospital care, especially since the current package does not include emergency services for trauma.
However, our study has several limitations. First, we did not directly measure changes in mortality. Our small sample size and poor health system infrastructure limit the capacity to follow an injured victim across the continuum of care. Second, skill and equipment use may have been over-reported by participants. Although we attempted to address this using prospective encounter records, hospital-level outcomes data would have increased the rigor of our study. Third, our study design may not be ideal. While a randomized controlled trial is the gold standard to prove intervention effectiveness, its use to test the benefits of essential skills of basic trauma care in the prehospital setting is not ethical. Furthermore, we did not use a control group in this study and relied on before-and-after comparisons to establish effectiveness which may be less than ideal.
Other contextual factors may have also affected our results. We could not control for changes in the frequency of skill use based on changes in job posting. Police trainees are rotated periodically, which removes them from active field duty, and thus potentially limits their ability to be present at emergencies. During the study, more trainees reported being unable to assist in emergencies due to work or travel related reasons suggesting that trainee selection was not ideal or that opportunity costs prohibited our trainees from responding to emergencies. Finally, the implications of some of our results remain unclear. Some skills, such as safe lifting and moving, were reported less frequently at six months than after the initial training perhaps because their new knowledge or increased credibility as emergency providers allowed them to harness help to transfer victims in emergencies or perhaps this skill simply may need more emphasis in future training.
Our cost and cost-effectiveness analyses must be interpreted with caution, even though sensitivity analyses were used. Estimates of the number of lay first-responders needed for Kampala and their potential impact on mortality were determined based on work primarily in a conflict-affected setting. By comparison, a decreased incidence of trauma and associated frequency of skill use in urban Kampala may have led to an overestimate of the cost-effectiveness.
Despite study limitations, many areas for further research exist. Better methods are needed to measure the impact of training lay first-responders on trauma morbidity and mortality. While we established the need for a simple first-aid kit for effective provision of prehospital care, mechanisms to ensure restocking of kits also need to be determined. Facility-based records could more accurately measure economic burden and may help determine the accuracy of our projections.
Training lay first-responders may be a critical and cost-effective first step to develop a formal emergency medical system. However, this intervention needs to be complemented by a second-tier of responders, a call center, and appropriate transportation mechanisms as well as facility-based training for clinicians to provide appropriate trauma care when victims reach health facilities. The precedent for such comprehensive trauma systems development is being established in other resource-constrained settings and could provide practical lessons for Ugandan policy-makers 
. Since injury disproportionately affects the working poor who rely on high-risk modes of transport such as non-motorized vehicles, motorized two-wheeled vehicles and foot traffic, by improving access to emergency services, a formal prehospital emergency system in Uganda can become a ‘pro-poor’
strategy and increase equity 
. Additionally, organized emergency services could improve health system efficiency by building on existing informal mechanisms of care. Most importantly, the global health community must urgently provide greater priority and resources for injury intervention research in resource-constrained settings that are particularly burdened with high incidence of trauma.
In conclusion, a lay first-responder training program is a practical and effective first-step towards developing a formal emergency system in Uganda. It is likely to be very cost-effective in this setting. Establishing and scaling up this intervention with in Kampala should be a key priority for Ugandan policy-makers. Incorporating emergency services into the essential package of health care would critically address the disproportionate global injury burden shouldered by the poor. Results of this program could be useful in other resource-constrained settings that lack emergency medical systems.